1. Field of the Invention
The present invention relates in general to intake devices of an internal combustion engine and more particularly to intake devices of a type that comprises an intake control valve installed in an intake tube of each cylinder of the engine. More specifically, the present invention is concerned with the intake device of such type that enhances a gas flow in each combustion chamber.
2. Description of the Related Art
As is known, for improving combustion of an internal combustion engine, more specifically, for assuring a stable combustion of a lean air/fuel mixture, it is effective to enhance a gas flow in the-combustion chamber. Swirling and tumbling effects are those that enhance the gas flow in the combustion chamber.
One of intake devices of an internal combustion engine that enhances such gas flow is disclosed by Japanese Laid-open Patent Application (Tokkai) 2004-124835. In the device disclosed by the publication, a passage is provided which extends from a diametrically one part of a downstream portion of an intake port to the diametrically other part of an upstream portion of the same where a larger intake air flow is needed. With this, part of the intake air flowing along the one part of the intake port is forcedly led to the upstream other part of the same thereby to enhance the gas flow in the combustion chamber. Actually, with this measure, the tumbling effect is increased or enhanced.